Some telephone users can be given the option of having a portable number. A portable number, in North America, comprises a 3 digit area code and seven digit local number that identifies a telephone user. Traditionally, an area code and local number was specific to a particular location. If a telephone subscriber changed location, such as street address, or city, a different telephone number would be assigned to the subscriber.
In contrast, a portable number remains the same even if the subscribe moves and receives calls on a telephone set in an entirely different city or region. Thus a person could move from Washington, D.C., to San Francisco, and yet retain the same area code and 7 digit local number. This presents many advantages to telephone users. For example, friends, family and business associates would not have to learn a new phone number every time a person or business changed locations. As well, number portability may facilitate competition between local telephone companies, long-distance carriers, and cable companies. When a person moves to a different city, the portable number remains assigned to them. When they are called, the telephone switching system routes the call to the new physical location. Similarly, if the person moved to a third location, the number would remain assigned to them and any calls to that number would be routed to the third location.
However, portable telephone numbers may present new problems. For example, toll charges may apply to a called number that appears to the caller to be a local, non-toll number. Time zones may be traversed by the call and it may be inconvenient or impossible to receive a call or difficult to determine the time at the receiving location. This would be particularly true if the calling party did not know the physical location of the called party.
As well, even if the telephone number is not portable, the caller may find it useful to receive information such as the time at the location of the called number.
U.S. Pat. No. 5,341,413 to Hori et al issued Aug. 23, 1994 discloses communication equipment with a destination area on-line display function. Information relating the state, country, city or town to the dialled number is stored in customer premises equipment and connected to a telephone set or a facsimile machine.